[P003] Poster

12:10 PM - 1:00 PM JST(3:10 AM - 4:00 AM UTC)

[P02-193] Metabolic engineering of cyanobacteria for the photosynthetic production of 1,4-butanediol directly from CO₂

○Howard Chi Hao Lin¹, Ethan I Lan¹ (1. National Yang Ming Chiao Tung University (Taiwan))

Keywords:

Cyanobacteria,1,4-Butanediol,Photoautotrophic biosynthesis,Biological carbon fixation,Microbial production

Photosynthetic conversion of CO₂ to useful chemicals using cyanobacteria is an attractive approach to resolving energy and environmental challenges. 1,4-Butanediol (1,4-BDO), a vital precursor widely used in the synthesis of polymers and organic solvents, is predominantly produced from petroleum or heterotrophic fermentation. To enable direct autotrophic production of 1,4-BDO from CO₂, we initially constructed a strain capable of producing its precursor 4-hydroxybutyrate (4HB). However, severe growth retardation was observed in this 4HB-producing strain, which critically limited the production titer. This was likely due to the cellular toxicity caused by the intracellular accumulation of succinate semialdehyde (SSA). To alleviate SSA accumulation, we screened for an efficient alcohol dehydrogenase to catalyze SSA to 4HB. By further tuning the expression levels of upstream genes, we enabled the strain to sustain continuous 4HB production. Subsequently, we screened several carboxylic acid reductases (CAR), which catalyze a key step in converting 4HB to 1,4-BDO, for functional expression in cyanobacteria. The best performing CAR homologue was combined with 4HB production pathway, the resulting strain produced 1,4-BDO with a titer of 184 mg/L. These results represent the first photoautotrophic biosynthesis of 1,4-BDO, demonstrating the feasibility of using cyanobacteria as a sustainable platform for producing high-value C4 chemicals.